The following is an extract from "10000birds.com":
Our good friend the Mallard tends to hybridize more than any other duck, and has hybridized with at least 50 other species of ducks and geese. Aside from being apparently a naturally curious and sexually experimental soul, the explanation for the Mallard’s proclivity for hybridization probably stems from a number of factors - it is abundant throughout much of the northern hemisphere, it has many close relatives (many ducks in the genus Anas are genetically closely-related and appear to have only ’split’ (separated) from each other historically quite recently), and in urban settings like city parks where Mallards are often resident there is sometimes an oversupply of males who are ready to turn their undoubted energies towards females of whichever species happen to come too close…
Walter
